Mercury switch



Aug. 9', 1966 L. w. COOK 3,265,844

MERCURY SWITCH Filed April 25, 1963 2 Sheets-Sheet 1 INVENTOR.

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A TTORNEY Aug. 9, 1966 L. w. cooK 3,265,844

MERCURY SWITCH Filed April 25, 1963 3 Sheets-Sheet 2 FIG 7 INVENTOR.Zea/76rd if 600%, BY

MM 4 6 1M A TTORNE Y United States Patent 0 3,265,844 MERCURY SWITCHLeonard W. Cook, Warwick, RJL, assignor to General Electric Company, acorporation of New York Filed Apr. 25, 1963, Ser. No. 275,719 7 Claims.(Cl. 200-152) This invention relates to an electrical switch, .and moreparticularly, to a mercury button electrical switch.

Many examples of mercury switches may be found in the prior art. Thoseswitches most closely related to the present invention employ a mercurybutton as the circuit control element, with the button having a metallicor ceramic envelope containing a quantity of mercury and two contactelectrodes. When the switch is in an open position, the mercury isnormally separated into two pools, one contacting each electrode. As theswitch is moved to the closed position, the mercury forms a single poolwhich completes the circuit between the electrodes. Control over theseparation or joining of the mercury pools is typically exercised by anoperating means rotating the mercury button between the switch open andswitch closed positions.

One example of such a switch is shown in Sambleson Patent 2,142,154,assigned to the assignce of the present invention. As there discussed,provision must be made to contact the electrodes of the mercury buttonand to support the button for rotation. In the Sambleson switch, thesetwo objectives .are obtained by providing projections having partspherical surfaces on the resilient contact arms, which engagecomplementary part spherical depressions on either side of the mercurybutton, providing a ball and socket joint. While this switch assemblyhas performed satisfactorily, it has been found to have certaindisadvantages. For example, it is possible to incorrectly assemble themercury button so that the part spherical depressions are not properlyaligned on the true axis for button rotation. As a result, the buttonmay become canted in the switch assembly. This misalignment may lead topoor electrical contact of the button terminals with resultantoverheating, and excessive play between the mercury button and theoperating means, causing the operating means to become disengaged fromthe button and fail to move it properly.

As a further example, in assembling the Sambleson switch, the buttonmust be trapped between the resilient contact arms before the arms areinserted into the switch housing. This assembly procedure requires careand may be difficult to perform. Further, slight changes in the partspherical form of either the contact arms or the mercury button cangreatly change the location of contact between the two, affectingoperation.

The mercury switch of the present invention overcomes thesedisadvantages by assuring that the axis of rotation of the mercurybutton is placed on a predetermined axis and retained along that axiswith adequate electrical contact.

' This invention has .as one of its objects the placement of the axis ofrotation of the mercury button along a predetermined axis in a switchhousing and the retention of the button along that axis.

Another object is to permit ease of assembly for a mercury buttonswitch, with retention of the button in the assembled switch.

Another object is to assure continued adequate elec- Patented August 9,1966 "ice trical contact for the terminals of the mercury button, givinga long and reliable operating life.

In one form of the present invention these objects are attained byproviding within a switch housing resilient contact members forreceiving a mercury button, such as that disclosed in Cook Patent3,032,633, assigned to the assignee of the present invention. Thisbutton is of generally cylindrical form and has terminals protrudingalong the axis of the cylinder. These terminals serve both as contactelectrodes for the mercury held within the button and as trunnions forbutton rotation. Channel indentations are placed on the contact members,extending from an edge, to engage the terminals of the button and toprovide electrical contact and bearing surfaces which determine the axisof rotation of the button. The indentations are formed in a scoop shape,flared adjacent the edge of the contact, so that the button may beeasily placed in the housing and retained along the proper rotationalaxis by the cooperation of the indentations and the resilient force ofthe switch mounting bracket.

The present invention may be most clearly understood when described inconjunction with the accompanying drawings, in which:

.FIGURE 1 is a top view, partly broken away, of an assembled switch;

FIGURE 2 is an exploded perspective view of certain elements oftheswitch assembly;

FIGURE 3 is a side view, in partial section, of an assembled switch;

FIGURE 4 is the same as FIGURE 3, showing the operating means in anintermediate position;

FIGURE 5 is a cross-sectional view of the switch taken along the line 55of FIGURE 4;

FIGURE 6 is a view of a portion of a contact member showing a modifiedform of indentation; and

FIGURE 7 is a view of a portion of a contact member showing anothermodified form of indentation.

As shown by FIGURES 1-5, the switch may be assembled in a housing 10 ofan insulating material. The housing is of a generally rectangular shape,.and has an open side to permit insertion and assembly of the variousswitch elements. The open side of the housing is closed, in theassembled switch, by a mounting bracket 11. The elements of theassembled switch which are contained within the housing are an operatingmeans, or trigger 12, a mercury button 13, and two spaced contactmembers 14.

The exploded view of these elements shown in FIG- URE 2 makes clear therelationship and certain features of the trigger 12 and themercurybutton 13. As illustrated, the button 13 is of the type disclosed in thepreviously mentioned Patent 3,032,633. The metallic shell 15 of thebutton has an indexing slot 16 and terminals 17, one of which is shownin FIGURE 2. The indexing slot 16 serves several purposes, one of whichis to provide a means for the trigger 12 to engage the button. The sideof the trigger to be placed adjacent the button is formed as an arcuatesurface having a protrusion 18 which engages the indexing slot 16 andcauses the button to move with the trigger. The assembled relation ofthe trigger and button, in which the protrusion engages the indexingslot, is most clearly illustrated in FIGURE 3. The trigger 12 is alsoprovided with extensions 19 which are formed with two short planarsurfaces 20, 21 tangent to a cylindrical surface about the axis ofrotation of the mercury button, when the trigger and button are in theassembled relationship. These planar surfaces engage the lower surfaceof the mounting bracket 11 in the assembled switch. The resilience ofthe mounting bracket 11 is such that the trigger 12 is stable when oneof the planar surfaces 20, 21 is engaged by the bracket and unstable inany other position. The unstable, transient, position is illustrated inFIGURE 4. Thus, the planar surfaces 20, 21 cooperate with the mountingbracket 11, in the assembled switch, to provide a snap action,twoposition switch movement.

The protruding terminals 17 are of cylindrical form, and together definethe desired axis of rotation for the mercury button 13. The resilientforce of the mounting bracket 11 acting against the trigger 12, .and theengagement of trigger 12 with the button 13 are such that the triggerrotates as a unit with the button about this axis defined by thetrunnion terminals 17.

The contact members 14 are held within the housing by any suitable meanssuch as slots 22 formed in opposite end walls of the housing andprojections 23 formed on the bottom of the housing. The contact membersare identical parts, each of which is provided with a conventional screwterminal 24 for attachment of the external wiring. In order to assurethat the button is maintained on the correct axis for rotation in thehousing, each of the contact members is provided with a channelindentation 25, extending from an edge. The contact member may be of anH shape, as shown in FIG- URE 3, and, referring to that particulardrawing, the indentation extends downwardly from the upper edge of thecontact member across bar 26. While it is convenient at this point todescribe the features of the contact structure with reference to theparticular coordinate system of FIGURE 3 in which the trigger isdirected upwardly, it

must be recognized that the switch may be mounted in various otherpositions and the coordinate convention chosen will vary accordingly.

As may be noted from FIGURE 5, the indentations 25 of the contactmembers 14 are struck outwardly so that when the contact members arepositioned in the housing, the convex side of the indentation faces thenearest housing wall. In order to facilitate insertion of the button 13during assembly of the switch, the indentations 25 are also given ascoop shape opening upwardly so that, when the contacts are assembled inthe switch housing, the upper end of the indentation, adjacent the edge,is flared outwardly to closely approach the housing wall. Carefulplacement of the contact members 14 in the housing 10 will permitalignment of the indentations 25 on the members along any desired axis.As this alignment is determinative of the location of the trunnionterminals 17, it is also determinative of the axis of rotation of boththe mercury button 13 and the trigger 12 in the assembled switch. It isnecessary that the contact members be correctly positioned within thehousing by such means as the slots 22 and projections 23 formed with thehousing.

The exact construction of the indentation is most clearly shown inFIGURE 2 which shows a channel indentation 25 extending downwardly froman edge of a contact member 14, with the indentation having a scoopshape opening upwardly. The lower end of the indentation 25 is struckalong a straight line generally parallel to the edge of the contactcross-bar 26 and is sharply stamped so as to provide a ledge 27perpendicular to the principal plane of the contact material, having adepth equal to the thickness of the stock material from which thecontact member is formed. The side surfaces 28 of the indentation,although not so sharply struck as to cut the stock material, are stampedso that they are generally perpendicular to both the principal plane ofthe stock material and the ledge 27, and generally parallel to eachother. The distance between these side surfaces must be at least asgreat as the maximum cross-sectional dimension of the trunnion terminals17, to allow admission of the button, but preferably does notsubstantially exceed such dimension. Stamping these side surfaces of thein dentation in this manner assures additional resistance to dislodgingthe trunnion terminals 17 from the indentations 25 due to the possibledevelopment of any twisting forces on the button. The resilience of thecontact members 14, which are bowed outwardly by inserting the button 13into the slightly scoop-shaped indentations 25, provides a force actingalong the axis of rotation.

In assembling the mercury button switch from these components, contactmembers 14 hearing indentations are first placed in the insulatinghousing 10. The mercury button 13 is then inserted and pushed downwardlywith the terminals 17 entering the indentations fully. These trunnionterminals thus bear against ledge 27 of each of the contactindentations, which provide a bearing surface about which the rotatingparts of the switch assembly move. The trigger 12 is then placed inengagement with the mercury button, with the protrusion 18 engagingindexing slot '16, and the mounting bracket 11 is secured to the housingto complete the assembly. When the mounting bracket 11 is secured to thehousing 10, the bracket brings into play a resilient force actingdownwardly upon the planar surfaces 20, 21 of the trigger. Thisresilient force presses the trunnion terminals 17 of the mercury button13 against the ledges 27 of the contact members 14 assuring that thebutton rotates about the desired axis, maintaining the button inalignment with this desired axis, and generating a high contact pressurebetween the trunnion terminals 17 and the ledges 27 by which theelectrical resistance of the assembly is kept low. The resilient forcealso prevents the trigger protrusion 18 from becoming disengaged fromthe button index slot '16 thus assuring that the mercury button willalways move with the trigger as desired.

The resilient mounting bracket 11, then, performs a multiplicity offunctions in the assembled switch. First, it provides the conventionalmounting for placing the assembled switch in a use location. Secondly,it provides a resilient force which, acting against the trunnionterminals of the mercury button, retains the mercury button in thedesired position within the switch assembly and assures good electricalcontact. Thirdly, the mounting Ibracket provides a resilient forceacting against the switch trigger to prevent the trigger from becomingdisengaged from the button. Finally, as the resilient force acts againstthe planar surfaces 20, 21 of the trigger extensions, a snap actionoperation is provided for the switch.

It may be seen that the contact members with the indentations of thepresent invention cooperate with a mercury button having axial terminalprotuberances in the switch assembly to assure adequate electricalcontact for the button terminals and to assure that the button rotatesabout the desired axis of rotation. With the indentation formed as shownin FIGURES 2 through 5, ease of insertion of the button during themanufacturing process is attained by the scoop-shaped indentation 25while the ledge surface 27 serves to determine the axis of rotation ofthe button and provides an electrical contact area. Retention of theterminals of the button against the ledges 27 is achieved by use of theresilient mounting bracket 11, acting against the trigger 12 and urgingbutton 13 downwardly.

The modified indentation 29 of FIGURE 6 is initially formed in a contactmember 30-similar tocontact member 14 of FIGURE 2. A slot 31 is thenformed in the indentation, extending from the upper end of theindentation downwardly toward the ledge 32.

This modified indentation form provides the ease of assembly advantagesand bearing and eelctrical contact surface characteristics of the firstindentation type. Additionally, the slot 31 provided in this modifiedform of indentation permits a slight vertical flexure of the contactmember cross bar under the single downwardly directed resilient force ofthe mounting bracket 11. This flexure makes it possible for the switchassembly to adjust to the small manufacturing tolerance variations whichare encountered in mass produced items.

The modified contact member of FIGURE 7 embodies the form of theindentation illustrated in FIGURE 2, in that a scoop-shaped indentation33 and a ledge 34 are used. In addition, a boss 35 is struck in theindentation counter to the direction in which the major indentation 33is struck. Thus, if the contact member is to be placed in the switchhousing 10 so that the major indentation has its convex side toward thenearest housing wall, the boss 35 is so placed as to have its convexsurface directed inwardly, toward the center of the housing.

This modified contact indentation form has the manufacturing advantages,bearing and electrical contact surface characteristics of theindentation form shown in FIGURE 2. In addition, the provision of theboss 35 introduces a further safeguard against dislodging the terminals17 of the mercury button from the desired position, thus providingadditional assurance that the button will be retained along the desiredaxis of rotation. This is additionally advantageous during the assemblyprocedure for the switch or under the possible situation in which theresilient mounting bracket 11 is removed or accidentally loosened.

While the present invention has been described with some particularity,it is to be understood that this is done for illustrative purposes onlyand the proper scope of the invention is to be determined solely fromthe appended claims.

What I claim .as new and desire to secure by Letters Patent of theUnited States is:

1. In a mercury switch (a) ahousing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supportingsaid button for rotational movement about an axis defined by saidterminals,

((1) each of said contact members having an indentation extending froman edge thereof,

(e) said terminals being received in said indentations,

and

(f) means for urging said terminals into engagement with said contactmembers.

2. In amercury switch (a) ahousing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supportingsaid button for rotational movement about an axis defined by saidterminals,

((1) each of said contact members having a principal plane and having anindentation extending from an edge thereof,

(e) each of said indentations terminating, at the extremity from saidedge, in a ledge perpendicular to the principal plane of said contactmember,

(I) said terminals being received in said indentations,

and

(g) means for urging said terminals into engagement with said ledges.

3. In a mercury switch (a) a housing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supportingsaid button for rotational movement about an axis defined by saidterminals,

(d) each of said cont-act members having a channel indentation extendingfrom an edge thereof,

(e) said channel indentation having two parallel side surfaces spacedapart a distance at least as great as the maximum cross sectionaldimension of said terminals, and terminating, at the extremity from saidedge, in a ledge perpendicular to said sides,

(f) said terminals being received in said indentations,

and

(g) means for urging said terminals into engagement with said ledges.

4. In a mercury switch (a) ahousing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supportingsaid button for rotational movement about an axis defined by saidterminals,

(d) each of said contact members having a principal plane and having achannel indentation extending from an edge thereof,

(e) each of said channel indentations having side surfaces generallyperpendicular to the principal plane of said contact member,

(f) each of said channel indentations terminating, at

the extremity from said edge, in a ledge perpendicular to the principalplane of said contact member and said side surfaces,

(g) said terminals being received in said indentations,

and

(h) means for urging said terminals into engagement with said ledges.

5. In a mercury switch (a) a housing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supportingsaid button for rotational movement about an axis defined by saidterminals,

(d) the ends of said terminals having plane surfaces perpendicular tosaid axis,

(e) each of said contact members having a principal plane and having anindentation extending from an edge thereof,

(f) a portion of each of said indentations, adjacent the extremity ofsaid indentation from said edge, lying in a plane parallel to theprincipal plane of said contact member,

(g) said terminals being received in said indentations,

and

(h) means for urging said terminals into engagement with said contactmembers.

6. In a mercury switch ('a) .a housing,

(b) a mercury button having aligned axially protruding terminals,

(0) spaced contact members mounted within said housing for supportingsaid button for rotational movement about an axis defined by saidterminals,

(d) each of said contact members having an indentation extending from anedge thereof,

(e) each of said indentations having a slot extending from said edge andterminating at a distance from the extremity of said indentation atleast as great as the maximum cross sectional dimension of saidterminals,

(f) said terminals being received in said indentations, and (g) meansfor urging said terminals into engagement with said contact members.

7. In a mercury switch (a) ahousing,

(b) a mercury button having aligned axially protruding terminals,

(c) spaced contact members mounted within said housing for supportingsaid button for rotational movement about an axis defined by saidterminals,

(d) each of said contact members having an outwardly struck indentationextending from an edge thereof, References Cited by the Examiner (e)each of said indentations having an inwardly struck N boss spaced fromthe extremity of said indentation a U ITED STATES PATENTS distance atleast as great as the maximum cross sec- 3,054,878 9/1962 Wlley 200 152tional dimension of said terminals, 5 3,089,937 5/1963 Von HOOIn et al200-152 (f) said terminals being received in said indentations, 330997910/1963 Sheldon et 200.452

and

(g) means for urging said terminals into engagement ROBERT SCHAEFERPrimary Examiner with said contact members. H; HOHAUSER, AssistantExaminer.

1. IN A MECURY SWITCH (A) A HOUSING, (B) A MERCURY BUTTON HAVING ALIGNEDAXIALLY PROTRUDING TEREMINALS, (C) SPACED CONTACT MEMBERS MOUNTED WITHINSAID HOUSING FOR SUPPORTING SAID BUTTON FOR ROTATIONAL MOVEMENT ABOUT ANAXIS DEFINED BY SAID TERMINALS, (D) EACH OF SAID CONTACT MEMBERS HAVINGAN INDENTATION EXTENDING FROM AN EDGE THEREOF, (E) SAID TERMINALS BEINGRECEIVED IN SAID INDENTATIONS, AND (F) MEANS FOR URGING SAID TERMINALSINTO ENGAGEMENT WITH SAID CONTACT MEMBERS.